Attaching self-supporting emissive film to cathode support

Abstract

In one aspect of the invention a process for affixing a self-supporting film of emissive materials in a binder to a cathode support member to provide a cathode for a cathode ray tube includes the steps of depositing at least one drop of a liquid mixture containing a solvent for the binder of the film onto a cathode support member, contacting the liquid mixture with the self-supporting film, and preferentially evaporating the liquid mixture to cause the binder of the film to affix the film to the cathode support member. In another aspect of the invention, an improved liquid mixture for affixing a self-supporting film of emissive materials in a binder to a cathode support member includes at least two liquids miscible in all proportions with one liquid essentially a non-solvent and another higher boiling liquid a solvent for the binder of the film.

We claim: 
     
       1. In a process for fabricating a cathode for a cathode ray tube wherein a drop of solvent mixture is deposited onto a cathode support member, the solvent mixture is contacted by a self-supporting film which includes a binder and the solvent mixture is preferentially evaporated to effect centering of said film on and attachment of said film to the cathode support member, an improved solvent mixture comprising: at least two liquids miscible in all proportions with one liquid a non-solvent and another liquid higher boiling than said one liquid and a solvent for said binder of said self-supporting film.   
     
     
       2. The improved solvent mixture of claim 1 wherein said binder of said self-supporting film is soluble in one and essentially insoluble in the other of said two liquids. 
     
     
       3. The improved solvent mixture of claim 1 wherein one of the liquids is a non-solvent for said binder of said film and has a boiling temperature lower than the other liquid which is a solvent for said binder of said film. 
     
     
       4. The improved solvent mixture of claim 1 wherein one of said two liquids is water. 
     
     
       5. The improved solvent mixture of claim 1 wherein one of said two liquids is ethylene glycol monobutyl ether and said self-supporting film is an ethyl cellulose film. 
     
     
       6. The improved solvent mixture of claim 1 wherein one of said two liquids is a solvent for said binder of said self-supporting film, has a higher boiling temperature than the other of said two liquids, and slightly dissolves said binder of said film and affixes said film to said cathode support member. 
     
     
       7. The improved solvent mixture of claim 1 wherein one of said two liquids is water in the range of about 70 to 90% by weight of said mixture. 
     
     
       8. The improved solvent mixture of claim 1 wherein one of said two liquids is ethylene glycol monobutyl ether in the range of about 10 to 30% by weight of said mixture. 
     
     
       9. The improved solvent mixture of claim 1 wherein one of said two liquids is water and the other is ethylene glycol monobutyl ether and said self-supporting film is an ethyl cellulose film.